Incidence of loose bodies in an osteoarthritic hip

N. N. RAI*, P. D. SINEY# , P.A. FLEMING# and B.M. WROBLEWSKI#
*Institute of Orthopaedic Research & Fracture Surgery, Patna, India #The John Charnley Research Institute, Wrightington Hospital, Wigan, UK

Introduction Results

Discussion Conclusion References

In a prospective study of 75 consecutive primary Charnley low friction arthroplasties carried out for osteoarthritis, loose bodies were found in nine hip joints; an incidence of 12%. Whether their presence is the cause or the effect of the condition remains unclear. Their discoid or spherical shape suggests that they were free and had been subjected to sliding or rolling motion. Those of irregular shape may have remained partly attached within the capsule, or become confined to a space.

Keywords: arthroplasty, hip joint, loose bodies

J.R.Coll.Surg.Edinb., 46, October 2001, 274-276

INTRODUCTION

Unlike loose bodies in the knee, loose bodies in the hip joint do not attract the same attention. Whether this is due to the real or perceived rarity of the problem or inaccessibility of the joint is not clear. The association of loose bodies with synovial osteochondromatosis is well established. ^1-3 Santora et al (1990), described seven cases of loose bodies in adolescent hips without any apparent underlying pathology.⁴

Milgram (1977) published very comprehensive accounts of 119 loose bodies recovered from joints. ^5,6 He also suggested three possible mechanisms for their formation: fragmentation of joint surface, fracture of osteophytes or osteochondral nodule proliferation in the periarticular soft tissues. Histological examination suggested “...gradual growth in size and configuration... due to surface proliferative changes of chondroblasts and osteoblasts ... with cartilaginous layering in 86.6% ... and osseous layering in 79.8%”. Milgram (1997) also suggested that osteoblastic and osteoelastic differentation did not depend on blood supply but revascularisation did occur when free bodies became attached to the synovium.6 His findings offered differentiation between the free bodies and those that subsequently became attached. No details of the joints affected were given except a brief mention of the elbow and the knee joint in the text.

Recent advances in hip arthroscopy have been instrumental in allowing further investigation without the trauma of formal surgery. In a detailed review of 328 arthroscopies carried out for hip pain, loose bodies were found in 31 cases - an incidence of 9.5%.7 We report our results of a prospective study to establish the incidence of loose bodies in hip joints undergoing primary Charnley low-friction arthroplasty for osteoarthritis.

Figure 1: Pre-operative radiograph showing loose bodies (arrowed)

PATIENTS AND METHODS

Assessment of the patients included full history, clinical examination of the range of movements in the hip joint and a review of the antero-posterior radiographs, centred on the symphysis pubis, with special attention paid to appearances that might indicate the presence of a loose body.

Figure 2: Loose bodies retrieved from the hip joints at the time of surgery. Note the different sizes and shapes

At hip replacement trochanteric approach was used routinely. After dislocation of the hip and sectioning of the neck of the femur all areas of the hip joint and the capsule were examined for the presence of loose bodies. Their number, location and size was noted. The findings are shown in Table 1.

Table 1: Details of patients, underlying hip pathology, number, size, shape and location of the loose bodies O.A. = Osteoarthritis; D.D.H.= Developmental displacement of the hip

RESULTS

Seventy-five patients and seventy-five hips were included in the study. The patients mean age was 60 years and 6 months (range 32-76 years) and their mean weight was 80 kg (range 61-92 kg). None of the patients gave a history of true locking, as is usually associated with the loose bodies in the knee joint. Stiffness on starting activities after a period of rest was almost a universal complaint. At times the ‘stick-slip’ phenomenon was mentioned. This was invariably on weight bearing and was usually in conjunction with turning while load bearing on the affected hip.

Loose bodies were found in nine hips: five right, four left; five males, four females. In one hip, two loose bodies were present, the remaining eight hips contained a single loose body each. Eight of the loose bodies were found in the acetabular notch area and two in the postero-superior quadrant of the hip joint. The mean dimensions of the loose bodies was 10 mm x 18.8 mm; minimum 6 mm x 3 mm, maximum 45 mm x 18.8 mm (Figures 1 and 2). The shape of the loose bodies was discord in six, spherical in one and irregular in three cases.

DISCUSSION

We have found a 12% incidence of loose bodies in the hip joints of patients undergoing hip replacement for osteoarthritis. There was nothing in the history to suggest that the loose bodies were the primary cause of the clinical problems. If we accept Milgram’s suggestion that loose bodies come either from the articular surfaces or fractured osteophytes then we can speculate that, under the first scenario, damage to the articular surfaces may be the cause of arthritis. One the other hand, if the source is the fracture of the osteophytes then loose bodies can be assumed to be secondary to the degenerate changes. If there was a direct causal relationship between loose bodies and osteoarthritis then presumably a much higher incidence could be expected.

CONCLUSION

The aetiology of loose bodies in osteoarthritic hips merit further studies even if only for purely academic interest. The incidence of loose bodies was found to be 12% in hips undergoing primary low-friction arthroplasty. Removal of the loose bodies alone would have been unlikely to resolve our patients’ symptoms.

ACKNOWLEDGEMENT

Research supported by the Peter Kershaw and John Charnley Trusts.

REFERENCES

1. Friedman B, Caspi I, Nerubey J, Hiszar M, Ganel A, Horoszowski H. Synovial chondromatosis of the hip joint. Orthopaedic Review 1988; 17; 994-8
2. Postel M, Courpied JP, Augouard LW. Pathological synovial membrane. Rev Chir-Orthop 1987; 73: 539 - 43
3. Shpitzer T, Ganel A, Engelberg S. Surgery for synovial chondromatosis: 26 cases followed up for 6 years. Acta-Orthop-Scand 1990; 61: 567-9
4. Santora SD, Stevens PM, Coleman SS. Intra-articular loose bodies in the adolescent hips. Journal of Paediatric Orthopaedics 1990; 10: 261-4
5. Milgram JW.The classification of loose bodies in human joints. Clin Orthop 1977; 124: 282-91
6. Milgram JW. The development of loose bodies in human joints. Clin Orthop 1977; 124: 292-303
7. Baber YF, Robinson AHN, Villar RN. Is diagnostic arthroscopy of the hip worthwhile? A prospective review of 328 adults investigated for hip pain. J Bone Joint Surg Br 1999; 81B: 600-3

Copyright date: 11th July 2001

Correspondence: B.M. Wroblewski, The John Charnley Research Institute, Wrightington Hospital, Hall Lane, Appley Bridge, Wigan WN6 9EP, UK