CASE REPORT Patella Dislocation Association with Drop Foot Aamir H. Shaikh1, Ashraf Dawood2, G. Eswara Murthy2 and Andrew C. Macey2

ABSTRACT All limb injuries should be examined with complete documentation of neurovascular assessment as they are often ignored in the busy emergency department setup. This may lead to delay in such diagnosis during the treatment of limb injuries at a follow-up in orthopaedic clinics. Early diagnosis can help orthopaedic team to investigate and start treatment which may help in the recovery of such neurovascular injuries. We report a case of missed neurovascular assessment in the emergency department on a patellar dislocation of a young person leading to foot drop and sensory numbness in the deep peroneal nerve distribution, which improved completely within three and a half months with conservative treatment. This is also the first reported case of foot drop in association with patellar dislocation.

Key words: Foot drop. Patella dislocation. Neurovascular examination. Transient peroneal neuropathy.

INTRODUCTION Nerves injuries of different types may arise after fractures and dislocations.1 Knee injuries of varying severity have been linked to involvement of peroneal nerve leading to foot drop condition. A report of non- contact knee dislocation in a female basketball player involving the peroneal nerve has been made which resolved in 42 weeks.2 So far, no report of peroneal nerve injury has been made for patella dislocation and subluxation. The only report of transient neuropraxia of the saphenous nerve in patella dislocation was reported by Glesson et al.3

We report a transient case of deep peroneal neuropathy Figure 1: Patellar dislocation. leading to foot drop condition in young male after patella dislocation treated conservatively with full recovery. vascular involvement of the limb as this was missed in the emergency department. After splinting his knee in CASE REPORT the back slab, he was referred to fracture clinic. Two A 16-years-old male suddenly twisted his right knee days later in the clinic he was identified with foot drop during dancing with foot being fixed and therefore, along with swelling on his right knee and sensory deficit leading to a fall. He arrived in the emergency in the first web space between the first and the second department with an inability to bear weight on his right toe in the deep peroneal nerve distribution. There was leg. On examination, swelling and deformity of his knee no power (grade 0) in tibialis anterior and extensor noted. X-ray revealed lateral patella dislocation with no hallucis longus (EHL) as detected on modified MRC associated fracture (Figure 1), which was reduced under scale.4 Although, patella apprehension test was positive, sedation. There were no clinical features of ligamentous rest of the ligamentous knee examination was normal knee injury except tenderness at the medial side of apart from generalized knee swelling. He was continued quadriceps. This patient was initially managed by the in the knee cast. Later, he was reviewed after 10 days emergency doctor and there was no record of neuro- with noted improvement in tibialis anterior and EHL power as the knee swelling started to settle. He received cast treatment for a total of 3 weeks and thereafter, 1 Department of Orthopaedic Surgery, Royal College of Surgeons, changed to a foot drop splint which allowed him to start Ireland. with his physiotherapy regime. He showed remarkable 2 Department of Orthopaedic Surgery, Sligo General Hospital, improvement and his motor weakness completely Sligo Eire, Ireland. resolved (grade 5) in three and half months of Correspondence: Dr. Aamir H. Shaikh, 23 Hayworth Mews, conservative treatment. He did not require a nerve Ongar Park, Dublin 15, Ireland. conduction study as he started to show clinical signs of E-mail: [email protected] improvement in both sensation and power of his right Received February 08, 2011; accepted October 21, 2011 lower limb as early as first 10 days of injury.

182 Journal of the College of Physicians and Surgeons Pakistan 2012, Vol. 22 (3): 182-183 Patella dislocation association with drop foot

DISCUSSION There are reports of knee dislocation leading to Deep peroneal nerve arises from common peroneal temporary foot drop as trauma to the knee joint leads to nerve, which innervate short head of biceps femoris soft tissue compromise at the level of fibular neck muscle in thigh and lies laterally in the common neural causing injury to common peroneal nerve.2 We report sheath with tibial nerve until proximally in the popliteal isolated deep peroneal nerve neuropathy following fossa where this division is encountered. Exceptions in trivial twisting injury of the leg leading to lateral patellar this anatomical course have been documented.5 dislocation which was initially missed and subsequently The common peroneal nerve then travels across the discovered after 2 days at follow-up in the outpatient lateral head of gastrocnemius muscle giving out lateral fracture clinic run by orthopaedic team. This neuropathy cutaneous nerve of the calf supplying lateral aspect of recovered fully on modified MRC scale4 with power of the leg below the knee. At about the neck of fibula the 5/5 without consequences in three and half month of nerve becomes subcutaneous and divides into deep conservative treatment. mainly muscular branch so called deep peroneal nerve We recommend that an assessment of the complete and superficial branch mainly sensory to lower lateral neurovascular examination should be warranted to aspect of leg and dorsum of feet and toes. It is motor to identify such type of remote injuries after patellar dis- the muscles of peroneal (lateral) compartment of the location in the emergency department. leg. The small area of foot in between the first two toes is supplied by cutaneous branch from the deep peroneal nerve. REFERENCES Deep peroneal nerve innervates anterior compartment 1. Rosenthal RE. Emergency department evaluation of musculo- skeletal injuries. 1984; :219-44. muscles of the leg by travelling deep to the peroneus Emerg Med Clin North Am 2 longus. This nerve supplies tibialis anterior, extensor 2. Putukian M, McKeag DB, Nogle S. Non-contact knee dislocation hallucis longus, extensor digitorm longus, and peroneus in a female basketball player: a case report. Clin J Sport Med. 1995; tertius. These muscles control ankle dorsiflexion and 5:258-61. toes extension. In this case, there was a typical 3. Gleeson AP, Kerr JG. Patella dislocation neurapraxia: a report of involvement of deep peroneal nerve as sensation of two cases. Injury 1996; 27:519-20. touch, pin prick and temperature were involved in this 4. Bhardwaj P, Bhardwaj N. Motor grading of elbow flexion: is nerve distribution along with loss of power of ankle Medical Research Council grading good enough? J Brachial Plex dorsi-flexors and big toe extensor. Peripher Nerve Inj 2009; 4:3. Superficial peroneal nerve on the other hand travels 5. Prakash, Bhardwaj AK, Devi MN, Sridevi NS, Rao PK, Singh G. between the peroneal longus and brevis, the primary Sciatic nerve division: a cadaver study in the Indian population ankle evertors and innervates them. and review of the literature. Singapore Med J 2010; 51:721-3.

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