J. Anat., Lond. (1963), 97, 3, pp. 393-402 393With 2 platesPrinted in Great Britain

Facets and imprints on the upper and lower extremities offemora from a Western Nigerian population

BY E. L. KOSTICKDepartment of Anatomy, University College, Ibadan, Nigeria*

Bony facets and imprints, particularly of the femur, have been described by manyauthors. Their incidence in various races has been recorded by Charles (1893),Parsons (1914), Walmsley (1915), Pearson & Bell (1919), Meyer (1924 a), and others.Recently, Schofield (1959) describes them in the Maori femur. Most of theseauthors have used exhumed material, for which accurate records are rarely available.The state of preservation of exhumed material varies greatly, and if only a part ofthe skeleton is available sexing and ageing may be difficult or impossible. It isunsuitable material on which to base observations concerning, for example, precisebone markings, structure and texture. Dodgers (1931) has used fresh material ofknown age and sex. Fresh material allows observation of the cartilage coatedarticular surfaces, but not of the underlying bone.For the purpose of this study specially prepared bones (series A) were used. They

provided a standard of uniform osteological quality and served as a control for thestudy of the exhumed material (series I.D.H.), in which bone preservation variedgreatly.

MATERIALS AND METHODS

Observations have been recorded on two series comprising in all 738 adultfemora: series A from specially prepared skeletons and series I.D.H. from exhumedskeletons. All the material is in the skeletal museum, University College, Ibadan,Nigeria.

Series A (Table 1). This consists of the femora from complete skeletons, preparedfrom fresh undissected material in the department. The preparation is carried outin four stages:

(1) Initial stripping. The entire skeleton is stripped of all soft material. Dis-articulations are effected at occipito-atlantal, lumbo-sacral, hip, knee, ankle, tibio-fibular, sterno-clavicular, shoulder, elbow, wrist, radio-ulnar, and temporo-mandibular, joints. The parts are then placed in tap water in special containers.Maceration is allowed to proceed for 1 week at 105° F.

(2) Fine stripping. After maceration, the containers are emptied, with suitableprecautions to prevent loss of teeth, terminal phalanges, etc., and the bones arefine stripped of all maceration resistant material, chiefly collagenous.

(3) Boiling. After fine stripping the bones are boiled in soap and water for 1 hr.,following which they are dried and bleached in the sun.

(4) Immersion in 95 % alcohol degreasingg). They are then immersed in 95 %* Present address: University of Saskatchewan, Saskatoon, Canada.

Anat. 9726

394 E. L. KOSTICK'industrial spirit' for 48 hr., again dried and bleached in the sun. The procedure isrepeated, this time immersing the bones in alcohol for only 24 hr.

This process gives clean dry bones. They sometimes retain their articular cartilage(P1. 1, fig. 4). The teeth are replaced in their appropriate sockets.Number, sex, tribe, and age are recorded. Some of the subjects have hospital

records. Unfortunately, the stated age is unreliable, since registration of births isnot compulsory. An attempt is made to confirm and estimate the age, by noting:(1) the appearance of the body prior to maceration; (2) the degree of ossificationand epiphyseal fusion; (3) the state of eruption and attrition of the teeth. InNigerians, the molars usually erupt before 21 years (commonly 16-17 years).Marked attrition may be present as early as 30 years. Thus it is only possible togive an approximate estimated age; they were mainly young adult. In 143 'stated'ages the average was 35-13 years (S.D. 8.56).

Table 1. Tribe, sex and side of the femora in Series A

Male Female Male and Female

Tribe Left Right Left Right Left Right

Yoruba 115 115 59 59 174 174Hausa 22 22 22 22Ibo 7 7 3 3 10 10Benin 5 5 3 3 8 8Calabar 2 2 - 2 2Unknown 58 58 8 8 66 66Total femora 209 209 73 73 282 282

In series A observations have been made on 209 pairs of male and 73 pairs offemale femora, giving a total of 564 femora.

Series I.D.H. This consists of the femora from skeletons, exhumed from thecemetery of the old Infectious Diseases Hospital, Ibadan, which was excavated tomake way for the present University College Hospital. A cemetery plan has beenavailable but there are no records of age, tribe or sex. The material has been sexedfrom accepted typical sex characters of innominate bone, skull, sternum and limbbones. Since most parts of the skeleton are present, a reasonable assessment of sexhas been possible. Like series A, series I.D.H. is estimated to be mostly early adult,below 40 years of age.

In series I.D.H. observations have been made on 15 left and 15 right femalefemora, and 73 left and 71 right male femora giving a total of 174. In addition toseries A and I.D.H. a collection of 238 foetal and young skeletons has been examined.Fresh knee and hip joints have been dissected and observed. Use has also beenmade of dissecting room material.

TERMINOLOGY

The articular lamella is cortical bone which underlies the articular cartilage(Johnston, Davies & Davies, 1958).

Facets and imprints offemora 395

OBSERVATIONS

(1) Facets and imprints at the upper end of the femurPoirier's facet (PI. 1, figs. 1, 3-5). This is a facet produced by an extension of the

articular surface of the head on to the anterior surface of the neck. Sometimes aridge, known as the cervical eminence, runs from the femoral tubercle (superiorcervical tubercle), along the antero-superior aspect of the neck, to the head. Whenit extends on to the medial end of the ridge the facet is prominent (see Testut, 1904).If the ridge is absent Poirier's facet is likely to be lacking also.

In some specimens in series A it is obvious that articular cartilage extends on tothe facet. The presence of cartilage is often taken as a prerequisite for a Poirier'sfacet but this is not the original description (Poirier, 1911; Odgers, 1931; Schofield,1959). In conformity with these and other authors a continuity of the articularlamella on to the neck is taken as acceptable evidence of a Poirier's facet. It mayalso occur with an imprint as shown in PI. 1, figs. 3 and 5.

Anterior cervical imprint (PI. 1, figs. 2, 5). This occurs on the anterior and inferioraspects of the medial part of the neck, adjacent to the head. It is also known as thefossa of Allen, the imprint of Berteaux, and sometimes again ascribed to Poirier.For the present study, it has been convenient to divide these imprints into two types,A and B. A somewhat similar division is given by Pearson & Bell (1919). Odgers(1931) differentiates three types: depressions, slight erosions, marked erosions.Type A. This is an ulcer-like excavation, exhibiting a floor and edges. In some

cases it has a clean punched-out appearance, with sharp edges and a depressedfloor; in others it is more irregular. The distal edge, that is the edge of the imprintaway from the femoral head, may be more prominent, making a transverse ridgemore or less parallel to the trochanteric line. This is Walmsley's (1915) capsularridge (P1. 1, fig. 2). The ridge divides the neck into a medial and a lateral portion,each with a bony surface of differing texture. Meyer (1924a) describes the ridgeas being congruent with the bony acetabular rim, since it resembles this in shape.When the dry bones are articulated the ridge acts like a 'door-stop'.The floor of the imprint may show various bony appearances: (1) trabeculated,

(2) finely honeycombed like cancellous bone, (3) very smooth, and (4) very rarelyhypertrophic usually in association with a periarticular osteoarthritis. The abovefeatures are also present on exhumed material and are not the result of violentmaceration.

Type B (P1. 1, fig. 3). This is a pleomorphic type, presenting as a discontinuity inthe normal bony appearance of the neck, and unlike type A it is not definitelycircumscribed. It may show a 'moth-eaten' or worn cancellous appearance, asthough the cortical bone had been gradually erased. This seems to occur only inyoung bones, 14-22 years, when epiphyseal union is present. It is situated on theantero-inferior aspect of the neck adjacent to the epiphyseal margin. When a largeseries of bones are examined one is left with the impression that this teenageimprint is a precursor of the ulcer type. This would agree with Odgers's (1931)observation that the imprint deepens with age.

Posterior cervical (acetabular) imprint (PI. 1, fig. 6). This has been noted par-ticularly by Walmsley (1915), as a facet resembling Poirier's, occurring on the

26.2

posterior aspect ofthe neck. Itmay be limited laterallyby a tubercle which sometimesborders the medial edge of the shallow groove for the obturator externus tendon.

Other facets and imprints. Schofield (1959) describes, in the Maori femur, acrescentic depression surrounding the antero-superior margin of the fovea. Thisperifoveal depression had been observed on a number of bones. When well markedit is C-shaped, the arc of the C on a radius about 1-3 cm. from the centre of thefovea. The open part of the C points towards the lesser trochanter. The fovea,almost always oval, has an everted lower lip like a lightly marginated spout, thetip of which also points to the lesser trochanter. It appears that the C-shapeddepression is due to an unduly prominent margin of the acetabular fossa. However,Little, Pimm & Trueta (1958) show the inside of the C as the non-weight-bearingcartilage. In this respect it is interesting to observe that the articular lamella inthe floor of the depression is thin and often shows fine perforations.The eversion of the foveal margin is due to the ligamentum teres as it ascends

vertically into the fovea. This eversion was present in foetal and young material.In the 5-month foetus or younger the fovea is a notch in the postero-inferior marginof the head.

(2) Facets and imprints on the lower end of the femurCharles's facet (PI. 2, fig. 7). This is a smooth facet above and behind the medial

epicondyle and extending to the adductor tubercle. Pearson & Bell (1919) have haddifficulty in defining it and exclude it from their series. In the present series thedesignation of Charles's facet was limited to a facet on the lower epiphysis (P1. 2,fig. 7), bounded above and laterally by the epiphyseal line. It may continue on tothe neighbouring shaft; its cartilage is continuous with the articular cartilage of thecondyle and that of the tibial imprint described below.The facet is for that part of the gastrocnemius bursa which usually communicates

with the joint with further extension into the overlying bursa of the semimem-branosus. Frazer (1948) shows the area as part of the origin of the medial head ofthe gastrocnemius. The presence of cartilage would suggest a bursa rather than amuscle origin. However, in young and foetal bones, the site of Charles's facet gaveorigin to part of the medial head of the gastrocnemius. This would suggest that thegastrocnemius is forced on to the capsule and neighbouring shaft by the growingbursa (but see Wood Jones, 1944).

Tibial imprint (P1. 2, figs. 7, 9, 13). This is on the posterior aspect of the lowerextremity of the femoral diaphysis, usually most marked above the medial condyle.More rarely it occurs above the lateral condyle. Above the medial condyle itborders on Charles's facet and their cartilages may be continuous, as describedabove. It usually presents as a depressed 'thumb-print' impression unlike the'punched-out' cervical imprint.Occasionally there is another 'thumb-print' impression in the tuberculated

roughness for the medial head of the gastrocnemius. Its causation is puzzling; itcould be due to a contained fabella forced against the popliteal surface in an acutelyflexed knee joint. This is suggested despite the fact that fabellae are twice as com-mon on the lateral side, and, in the fully ossified form, nine times more common onthe lateral than the medial side.

396 E. L. KoSTICK

Facets and imprints offemora 397Osteochondritic imprint (P1. 2, figs. 7, 13). At this point it is convenient to record

a remarkable feature in series A. The upper posterior part of the lateral condyle ofcertain femora shows either a hole or plaque-like bony excrescence. Sometimes it isof pin-hole size, at other times it is a cavity filled with bony debris and floored withsclerotic bone. The articular lamella is always primarily affected. The cartilage isusually flattened or worn at the site; this is best seen in the fresh specimen. Thefemoral condyle is often facetted or flattened at the site of the lesion. It is usuallybilateral, occasionally occurring with a similar lesion on the posterior part of themedial condyle. The lesion occurs at the place of contact between the tibial andfemoral condyles in the acutely flexed knee joint. Such flexion normally occurs inthe squatting position. It is suggested that this is an osteochondritis dessicans ofthe adult type (Smillie, 1960) (see PI. 2, fig. 7). This is a hitherto undescribed site forosteochondritis dessicans in the knee joint in current literature. Its incidence isgiven in Tables 3 and 4. Further description and the consideration of its aetiologyare beyond the scope of this paper.

Martin'sfacet (P1. 2, fig. 10). This is a crescentic facet formed by extension of thetrochlear surface on to the lateral aspect of the lateral condyle, sometimes givingthe lateral trochlear margin a bevelled appearance. It is present in varying degreein nearly all the femora.

Table 2. Approximate percentage incidence of anterior acetabular imprintsand Poirier's facet

Series A Series I.D.H.A A

L. R. L. and R. L. R. L. and R.

Type A or B Male 29 29 29 59 56 57ant. cervical Female 45 45 45 50 53 52imprint Male and female 33 33 33 58 55 56

Ulcer. Male 12 10 11 33 30 32Type A Female 20 22 21 29 33 30imprint Male and female 14 13 14 33 30 32

Pleomorphic. Male 17 19 18 25 25 25Type B Female 25 23 24 21 20 20imprint Male and female 19 20 20 25 25 25

Poirier's Male 57 55 56 71 76 72facet Female 38 38 38 46 58 52

Male and female 52 51 51 67 73 70

Supratrochlear facet and imprint (PI. 2, fig. 11). The facet is produced by theextension of the superior margin of the lateral trochlear surface on to the neighbour-ing shaft. It is at or just above the point of maximum anterior projection of thelateral condyle. Instead of a facet an imprint or tuberosity may be present. Whenthe imprint is marked, it conforms somewhat to the suprapatellar imprint or fossadescribed by Meyer (1924b) (P1. 2, fig. 11). It is almost always bilateral, occurringat the site at which an osteochondritic lesion may be expected.

Peritrochlear groove (PI. 2, fig. 8). Sometimes the medial trochlear margin israised, forming the edge of a gutter-like groove, in which run periarticular vessels.

398 E. L. KOSTICKIt becomes deeper and almost converted into a tunnel in a periarticular osteo-arthritis. It extends from the supratrochlear area (often depressed) to a notchusually present which demarcates the trochlea from the condylar surface (PI. 2,fig. 8).

Table 3. Data and approximate percentage offemora with an osteochondriticimprint in series A

Female Male Male and female

L. R. L. L. R. L. L. R. L.and R. and R. and R.

Total femora 73Osteochondritic imprint 20Approximate percentage 27

73 146 209 209 418 282 282 56423 43 48 52 100 68 75 14331 29 23 25 24 24 27 25

Table 4. Data offemora in series A and I.D.H.

Series A Series I.D.H.KA A, A

A

Female Male Female Male

L. R. L. L. R. L. L. R. L. L. R. L.and R. and R. and R. and R.

Total femora ... 73 73 146 209 209 418Poirier's Facet 28 28 56 119 115 234*D

Types A or B cervical imprints 33 33 66 61 60 121D

Ulcer type A imprint 15 16 31 26 21 47D

Pleomorphic type B imprint 18 17 35 35 39 74D

Poirier's facet or imprints 52 54 106 177 172 349D

Post. acetabular imprint 9 9 18 18 20 38D

Martin's lat. cond. facet 53 49 102 172 170 342D

Tibial imprintD

Trochlear 'gutter'D

Supra-trochlear facetD

36 39 75 77 69 146

9 9 18 21 27 48

25 28 53 68 70 138

15 15 30 73 71 1446 7 13 48 48 962 3 5 5 8 137 8 15 42 39 811 1 2 1 34 5 9 24 21 451 1 2 1 33 3 6 18 18 361 - 1 2 1 39 9 18 64 61 1251 1 2 4 8 121 5 6 8 10 18

9 9 18 58 56 1144 8 7 9 12 216 6 12 23 23 461 1 2 - -

Nil Nil Nil 9 9 187 7 14 18 17 353 4 7 30 32 627 7 14 18 17 35

* D means determination was impossible. Thus out of 15 left female femora determination was impossible intwo. Percentage incidence as given in the text in these cases was calculated by subtracting the number ofindeterminable bones. For example, the percentage calculation for this example based on 6/13 left femora was46% approximately.

Facets and imprints offemora 399

(3) Incidence offacets and imprintsDetailed data for the features described are given in Table 4. The percentage

incidence of the cervical imprints and facet are given in Table 2. Poirier's facet ismore common in the male. The cervical imprints are more common in the female.The crescentic perifoveal depression is well marked in only two pairs of femora in

series A, but is present to a lesser degree in 22 femora. In series I.D.H. it occurs inonly eight cases.The tibial imprint occurs more often in the female (51 %) than male (35 %) in

series A, there being no significant difference on the right and left sides. Charles'sfacet occurs in almost all the femora.The osteochondritic imprint (Table 3) is more common in the female. This is not

the usual sex ratio (Aegerter & Kirkpatrick, 1958). In ten bones it is present onboth medial and lateral condyles, only in one bone (left) does it occur on the medialcondyle alone, but its right partner has imprints on both condyles. Five cases onlyoccurred in series I.D.H.

Martin's lateral condylar facet is slightly more common in the male, 82 %, thanfemale, 71 %, there being no significant difference on the two sides.

In conclusion, facets are more common in the male, imprints more common in thefemale. Series I.D.H. shows a greater incidence of facets and imprints. It shouldbe pointed out that the percentages calculated for the female in series I.D.H. arebased on only 30 bones, not all of which are suitable for the precise study of bonemarkings (Table 4).

DISCUSSION

These investigations show that: (1) the sequelae of squatting in the form of bonechanges (facets and imprints) are more evident at the lower than at the upper endof the femur; (2) it is difficult to accept that imprints particularly of the neck aredue to postural factors. It is pointed out that, though most of the subjects werehospital cases, the bones themselves were normal.

Facets and imprints at the upper end of the femurIn extension of the hip joint the medial end of the cervical eminence which is the

site of Poirier's facet rubs against the capsule, especially the taut ilio-femoralligament. Extension of the hip joint is said to be greater in the male than thefemale (Frazer, 1948). Poirier's facet occurs more often in the male than female inmost series (Odgers, 1931). This is true of series A and I.D.H. Squatting involvesflexion of the hip joint. If it results from extension of the hip joint, Poirier's facetcannot be classed as a squatting facet (Pearson & Bell, 1919).The Nigerian commonly sits with knees flexed on a very low stool the seat of

which is 6 inches above the ground. The standard chair seat is 18 inches high, buteven when this is available the squatting stool is often preferred. It seems reason-able to assume that most of the subjects in the present series adopted such a squat-ting attitude. If imprints (type A and B) on the femoral neck are due to squattingone would expect to find a higher incidence in the squatting races: but, the incidencein series A was no higher than that in the non-squatting races.

400 E. L. KOSTICKA satisfactory explanation is thus required to account for the anterior cervical

imprint in squatting and non-squatting races. Its occurrence is difficult to correlatewith other postural factors in addition to squatting (Pearson & Bell, 1919; Meyer,1924a). Tension in the capsule varies with the position of the joint. The pull ofthe capsule is presumed to produce a local bone reaction, such as Walmsley'scapsular ridge. The arrangement of the fibres in the hip joint capsule is suchthat maximum tension exists in extreme flexion and extension (Meyer, 1934).Hence Odgers' (1931) suggestion that the cervical imprint and Poirier's facet aredue respectively to: (1) the spiral twist and full screw home of the circular fibresof the zona orbicularis; and (2) tension in the ilio-femoral ligament occurring onextension of the hip joint. If the cervical imprint is due to capsular pull, then itmay occur as a result of extension (as in walking or in standing) or of flexion (as insquatting) of the hip joint and also may account for its occurrence in non-squattingand squatting races.

Comparison of incidence of the cervical imprints with that of other investigatorsis difficult owing to subjective factors and differences in material studied (seeMeyer, 1934). Odgers (1931) used fresh material in which cartilage extension andcapsular relations are obvious, and found that Poirier's facet and cervical imprintare usually combined. But in the dry bones of series A and I.D.H. this is not thecase (see Meyer, 1924 a). Only 58 femora in series A have a Poirier's facet in com-bination with a cervical imprint. In series A, imprints are more common in thefemale. It is emphasized that series A is well prepared material, clean dry bone;Odgers's erosions involved soft tissue.

Facets and imprints at the lower end of the femurThe tibial imprint may be due to contact with the lateral part of the posterior

border of the medial tibial condyle and this part of the condyle often presents as aprominence or tubercle (tuberculum tendonis P1. 2, fig. 14) (Cave & Porteous,1958 a). On acute flexion this tubercle is driven into the imprint. Deep imprints areassociated with prominent tubercles. It appears that the posterior border of themedial condyle is reciprocally grooved (P1. 2, fig. 14) by the medial margin of theimprint. On dissection, however, it is evident that this vertical groove, whenpresent, is caused by the tendon of the semimembranosus just proximal to itsinsertion into the groove for the semimembranosus and the tuberculum tendonis(Cave & Porteous, 1958 b). P1. 2, fig. 14, shows the vertical groove and tubercle. Theimprint may be the result of pressure by this tubercle in acute flexion of the kneejoint. Such flexion occurs in the squatting position. The incidence is higher in thefemale, many of whom adopt the squatting attitude for long periods-buttocks onthe heels, knees apart-as a resting posture.The habit of squatting may be an explanation for the high incidence of Martin's

lateral condylar facet. It has been suggested that the facet is due to the quadricepstendon particularly that of the vastus lateralis as it glides over the lateral condylarsurface especially in full flexion of the knee joint. Frazer (1948) holds that thisexplanation is hardly justifiable because of the irregular occurrence of the facet.This may be true of English bones, but 80% of series A have a lateral condylarfacet. Thus Martin's (1932) original observations are supported by this investigation.

Facets and imprints offemora 401The patella tends to be displaced laterally in movements of the knee joint.

Habitual dislocation is a well-known clinical condition especially in the youngfemale. The tendency for lateral displacement is normally counteracted by theangulation of the lateral trochlear surface of the femur. It is likely that the supra-trochlear imprint or tuberosity is a bony reaction to the pressure exerted by thepatella due to the lateral displacement mentioned.

In conclusion the discrepancies between series A and series I.D.H. should benoted. The final result in series I.D.H. is affected by poor preservation of thematerial so that precise bone marking is impossible.

SUMMARY

1. Observations of facets and imprints have been recorded on 738 femora,mainly of the Yoruba people, of which 564 were specially prepared material, theother 174 femora being exhumed material.

2. Various facets and imprints are described and their incidence recorded. Afrequently occurring osteochondritic imprint on the lateral condyle was noted.

3. Postural factors are discussed, and are difficult to correlate with the imprintsat the upper end of the femur. Squatting is unimportant in this respect, there beingno greater incidence of cervical (acetabular) imprints than in non-squatting races.

4. The results of squatting are more evident at the lower end. Tibial imprintsare often present, and there is a high incidence of Martin's lateral condylar facet.

I am grateful and indebted to Prof. Alastair G. Smith, for the use of his materialand guidance. I would also like to thank Mr D. G. Stuart, F.I.M.L.T., for hispatient help with the photographs.

REFERENCES

AEGERTER, E. & KIRKPATRICK, J. A. (1958). Orthopaedic Diseases. Philadelphia and London:W. B. Saunders Co.

CAVE, A. J. E. & PoRTEous, C. J. (1958 a). The attachments of the m. semimembranosus. J. Anat.,Lond., 92, 638.

CAVE, A. J. E. & PoRTEous, C. J. (1958 b). A note on the semimembranosus muscle. Ann. R. Coll.Surg. Engl. 24, 251-256.

CHARLES, R. H. (1893). The influence of function as exemplified in the lower extremity of thePanjabi. J. Anat., Lond., 28, 1-18.

FRAZER, J. E. (1948). The Anatomy of the Human Skeleton. London: J. and A. Churchill Ltd.JOHNSTON. T. B., DAVIES, D. V. & DAVIES, F. (1958). In Gray's Anatomy, 32nd edition. London:Longmans Green and Co.

LITTLE, K., PiMM, L. H. & TRUETA, J. (1958). Osteoarthritis of the hip. An electron microscopestudy. J. Bone. Jt. Surg. 40B, 123-131.

MARTIN, C. P. (1932). Some variations of the lower end of the femur which are especially prevalentin the bones of primitive people. J. Anat., Lond., 66, 352-362.

MEYER, A. W. (1924a). The 'Cervical Fossa' of Allen. Amer. J. Phys. Anthrop. 7, 257-269.MEYER, A. W. (1924b). Patellar supracondylar fossae. Amer. J. Phys. Anthrop. 7, 271-273.MEYER, A. W. (1934). The genesis of the fossa of Allen and associated structures. Amer. J. Anat.

55, 469-510.ODGERS, P. N. B. (1931). Two details of the neck of the femur: (1) the eminentia, (2) the empreinte.

J. Anat., Lond., 65, 352-362.PARSONS, F. G. (1914). The characters of the English thigh bone. J. Anat., Lond., 48, 238-267.PEARSON, K. & BELL, J. (1919). A study of the long bones of the English skeleton. Part I. The

femur. Drap. Co. Mem. Biom. Ser. 10, 1-224.POIRIER, P. (1911). Traits d'anatomie humaine (Poirier & Charpy), vol. I. Paris: Masson et Cie.

402 E. L. KoSTICKSCHOFIELD, G. (1959). Metric and morphological features of the femur of the New Zealand Maori.

J. R. Anthrop. Inst. 89, 89-105.SMILLIE, I. S. (1960). Osteochondritis Dessicans. Edinburgh and London: E. and S. Livingstone.TESTUT, L. (1904). Traits d'anatomie humaine, 5th edition. Paris: 0. Doin.WALMSLEY, T. (1915). Observations on certain structural details of the neck of the femur.

J. Anat., Lond., 49, 805-318.WOOD JONES, F. (1944). Structure and Function as seen in the Foot. London: Bailliere, Tindalland Cox.

EXPLANATION OF PLATES

PLATE 1

Fig. 1. Right femur. Upper end, anterior aspect. Tip of pointer A in a Poirier's facet.Fig. 2. Left femur. Upper end, anterior aspect. Pointer A shows the 'Ridge' bounding theextensive imprint as marked by B.Fig. 8. Right femur. Upper end, anterior aspect. A shows a Poirier's facet in addition to the'teen-age' imprint shown by B. Note the epiphyseal line of the trochanter.Fig. 4. Left femur. Upper end, anterior aspect. Note cartilage is still on the head. A small tagabove and in front of pointer A extends into the facet.Fig. 5. Right femur. Upper end, anterior aspect. Poirier's facet shown by A, coexisting with anulcer-type imprint indicated by B.Fig. 6. Right femur. Upper end, posterior aspect. A shows a posterior facet (of Walmsley). Thegreater trochanter is broken above its fossa.

PLATE 2

Fig. 7. Left femur. Lower end. Posterior aspect. A shows a lateral tibial imprint, B a medialtibial imprint, C shows a typical osteochondritic imprint on the lateral condyle at the squattingsite. A Charles's facet is also shown at D.

Fig. 8. Left femur. Lower end. Oblique medial aspect. The pointer A lies along a peritrochleargroove.Fig. 9. Left femur. Lower end. Pointer A shows a thumb-print type of tibial imprint above themedial condyle.Fig. 10. Right femur. Lower end. Lateral aspect. Pointer A shows a Martin's facet.Fig. 11. Right femur. Lower end. Anterior aspect. A supra-trochlear fossa or imprint is shownby pointer A.Fig. 12. Left femur. Lower end. Anterior aspect. Pointer A shows upper lateral trochlear marginextending on to the shaft.Fig. 13. Right femur. Lower end. Posterior view. A shows a tibial imprint and B the bonyplaque in an osteoarthritis bone. Compare with Fig. 7.

Fig. 14. Left tibia. Upper end. Posterior aspect. A shows the tubercle which is received into thetibial imprint. B points to the groove caused by the semimembranosus.

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