AN ASSOCIATION WITH A PATELLAR SPUR

Rupture of the quadriceps tendon: AN ASSOCIATION WITH A PATELLAR SPUR

Hardy, J R W

We reviewed the records of 107 consecutive patients who had undergone surgery for disruption of the knee extensor mechanism to test whether an association existed between rupture of the quadriceps tendon and the presence of a patellar spur. The available standard pre-operative lateral radiographs were examined to see if a patellar spur was an indicator for rupture of the quadriceps tendon in this group of patients. Of the 107 patients, 12 underwent repair of a ruptured patellar tendon, 59 had an open reduction and internal fixation of a patellar fracture and 36 repair of a ruptured quadriceps tendon. In the 88 available lateral radiographs, patellar spurs were present significantly more commonly (p

Rupture of the quadriceps tendon following trauma is often missed. There is no radiographic indicator of the injury. The clinical diagnosis can be confirmed either by ultrasound or MRI. There may be a greater delay in the diagnosis of rupture of the quadriceps tendon than in other causes of extensor failure such as fracture of the patella and rupture of the patellar tendon as the latter are obvious on radiographs. Delay in surgical intervention may compromise recovery.

This paper examines whether an association exists between rupture of the quadriceps tendon and the presence of a patellar spur (Fig. 1), which is defined as a bony projection above the insertion of the quadriceps into the non-articular superior pole of the patella. Recognition of this association might improve the chances of diagnosis of rupture of the quadriceps tendon.

Patients and Methods

The operation registers of the orthopaedic trauma theatres from the Frenchay Hospital in Bristol were examined over a period between March 1990 and April 2004 to identify patients who had undergone repair of the extensor mechanism of the knee. The operations comprised repair of a rupture of the patellar tendon, open reduction and internal fixation of a fracture of the patella and repair of a rupture of the quadriceps tendon.

One hundred and seven patients were identified. The notes and available lateral radiographs of the injured knee were re-examined for demographic data, the mechanism of injury, the presence or absence of a patellar spur, its length, the length of the patella and of the patellar tendon. The latter measurements were used to confirm the diagnosis of rupture of the patellar tendon where there were no other radiographie indicators of failure of the extensor mechanism. The Insall-Salvati1 ratio was used pre-operatively as it allows for variations in the size of the knee and the radiographic projection; damage to the patellar tendon was inferred if the ratio exceeded 1.2. Associations were tested with chi-squared analysis using SPSS software (SPSS Inc., Chicago, Illinois).

Results

Of the 107 patients identified, 12 underwent repair of a ruptured patellar tendon, 59 open reduction and internal fixation of a fractured patella and 36 repair of the quadriceps tendon. The age distribution was similar for the three types of injury (Table I). Direct injury was a much more common mechanism in the patients with a fracture of the patella than in the other two groups (Fig. 2), and a greater proportion of these patients were male (Table II). There were no patients with bilateral rupture, evidence of renal disease, gout, or steroid use. The radiographs of 88 patients were available (Table III). All patients with rupture of the patellar tendon had an increased Insall-Salvati ratio. Those with rupture of the quadriceps tendon did not.

Table IV shows the distribution of the presence or absence of a patellar spur between the three types of injury. Subsidiary chi-squared testing indicated that the distributions were not significantly different between rupture of the patellar tendon and fracture (p = 0.312), and that the significant differences were between the rupture of the quadriceps tendon and the other two injuries (p = 0.0).

Of the 33 patients with spurs, 23 had rupture of the quadriceps tendon. Thus, in patients coming to surgery for painful failure of the extensor mechanism of the knee, the positive predictive value of the presence of a spur for rupture of the quadriceps tendon is 23 of 33 (69.6%). Of the 29 patients with rupture of the quadriceps tendon, 23 had spurs. Thus, the corresponding sensitivity of spurs in picking up a rupture of the quadriceps tendon is 23 of 29 (79.3%).

Discussion

Disruption of the extensor mechanism of the knee is a rare but serious injury.2 The three most common causes are fracture of the patella, rupture of the patellar tendon and at the quadriceps tendon. The latter injury is often overlooked. The outcome is best following early repair3-5 so prompt diagnosis is important. The radiographic appearance of a cranially-displaced avulsed part of the patella associated with the tendon should allow the diagnosis to be made.6 However, avulsion of this sort is unusual.

Reviews of the literature on unilateral quadriceps tendon rupture highlight problems in establishing the diagnosis in older patients.7,8 Bilateral tendon rupture is rare and is generally associated with chronic renal failure,9 gout,10 the use of steroids,11,12 quinolone antibiotics13 and diabetes. Bilateral tendon rupture associated with systemic disease, for example in renal failure, tends to be in the younger age group,9-11,14 and has been reported in patients between 16 and 22 years of age.15-17 None of our patients had these conditions or bilateral ruptures.

The predictive value of a spur for rupture of the quadriceps tendon must be considered in the light of the obvious selection bias of this cohort of patients chosen for operative repair. We accept that we do not know the prevalence of a patellar spur in the normal population. However, if it is as uncommon as rupture of the quadriceps tendon then the presence of a radiographically-identified spur should alert the examining doctor to the possibility of such an injury in patients with traumatic failure of the extensor mechanism.

We acknowledge Dr Andrew Black for his statistical advice on the analysis of our data.

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

References

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J. R. W. Hardy, M. Chimutengwende-Gordon, I. Bakar

From Frenchay Hospital, Bristol, England

* J. R. W. Hardy, MD, FRCS(Ed), FRCS(Eng), FRCS(Orth), Consultant Orthopaedics and Trauma

BUPA Hospital Bristol, 3 Redland Hill, Bristol BS6 6UT, UK.

* M. Chimutengwende-Gordon, MBChB, Senior House Officer

Horton Hospital, Oxford Road, Banbury, Oxfordshire 0X16 9AL, UK.

* I. Bakar, MB, ChB, MRCS, Registrar

Derriford Hospital, Derriford Road, Plymouth PL6 8DH, UK.

Correspondence should be sent to Mr J. R. W. Hardy; e-mail: john@johnhardy.co.uk

©2005 British Editorial Society of Bone and Joint Surgery

doi:10.1302/0301-620X.87B10. 16624 $2.00

J Bone Joint Surg [Br] 2005:87-8:1361-3.

Received 21 April 2005; Accepted after revision 10 May 2005

Copyright British Editorial Society of Bone & Joint Surgery Oct 2005

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