• Hip & Knee Conditions Clinical Trials
• Sports Medicine
• Orthopaedic Procedures

• Hip & Knee Conditions
• Orthopaedics Clinical Trials
• Orthopaedics
• Sports Medicine
• Orthopaedic Procedures

Steven B. Cohen, MD, Thomas Jefferson University, Philadelphia, Pennsylvania, USA, discussed the findings of a prospective study of patients who underwent reconstructive surgery of the anterior cruciate ligament (ACL) to understand the incidence of and characterize injury to the infrapatellar branch of the saphenous nerve (IBSN), as measured by numbness.

ACL reconstruction is a common procedure in sports medicine. While surgery is typically effective in restoring the degree of knee function needed for the rigors of athletic activity, numbness of the lateral portion of the knee is a complication regardless of the type of graft used. This complication arises because of injury to the IBSN, which is susceptible to surgery-related damage because of its transverse or oblique passage between the lower portion of the patella and the tibial tubercle. The outcome of the ACL reconstructive surgery, however, is generally not affected.

Despite the frequency of IBSN injury, the incidence is unclear. Estimates range widely from very low (.5% of cases) to very high (88% of cases) [Kjaergaard J et al. Int J Sports Med 2008; Mistry D, O'Meeghan C. ANZ J Surg 2005]. Injury can occur during harvesting of the hamstring [Sabat D, Kumar V. Knee Surg Sports Traumatol Arthrosc 2013] or during routine knee arthroscopy, and can occur irrespective of whether the incision is vertical, oblique, or horizontal [Kerver ALA, et al. J Bone Joint Surg Am 2013].

The current study sought to determine the incidence of numbness around the knee after ACL reconstructive surgery in 218 patients. Secondary aims were to subjectively assess if postoperative knee numbness persisted at 6 weeks and if the total area of numbness changed at 6 months or after 1 year. Patients completed a questionnaire at 6 weeks, 6 months, and 1 year after surgery and the numbness score was determined. Patient satisfaction with the outcome despite numbness was also queried. Table 1 summarizes the surgical variables in the patient population.

At 6 weeks, numbness in the inferolateral knee and along the distal midline was evident in 34% and 30% of patients, respectively. The use of an autograft was associated with an increased numbness score (average of 1.85 ± .60). Patient-reported numbness scores declined with increasing postoperative time (overall population −1.00 ± .16 at 6 months and −1.26 ± .18 at 1 year).

Linear-mixed-effects model analysis revealed that hamstring and bone-tendon-bone autografts were associated with 1.94 ± .52 times and 1.57±.51 times more numbness than were allografts, respectively. The two autografts did not differ significantly from each other. The length of the incision, the number of arthroscopic portals, and the presence of meniscus repair had no appreciable effect on numbness. At 1 year, numbness remained in one-third of patients, although, in general, the severity had lessened over the year.

The data from this study support the common occurrence of sensory deficits (ie, numbness) after ACL reconstructive surgery. The data also shows that the majority of deficits improved with time and resolved within 1 year. Numbness was more prevalent with autografts than with allografts.

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The editors would like to thank the many members of the 2014 American Orthopaedic Society for Sports Medicine presenting faculty who generously gave their time to ensure the accuracy and quality of the articles in this publication.

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