Incidence
Primary THR 0.3%
Revision THR 0.8%
Slaven et al J Arthroplasty 2023
- 10,000 primary THA
- incidence motor nerve palsy 0.3%
- posterior approach: 0.5%
- anterior approach: 0.2%
- 112,000 revision THA
- incidence nerve injury 0.8%
Risk factors
Christ et al J Arthroplasty 2019
- state database of 200,000 THA
- associations with nerve injury
- pre-existing spine conditions
- diabetes
- dislocation
- 27,000 primary THA
- DDH
- revision surgery
- post traumatic OA
- limb lengthening
Approach
Slaven et al J Arthroplasty 2023
- 10,000 primary THA
- posterior approach: 0.5%
- anterior approach: 0.2%
Nerves
Sciatic nerve / CPN
Femoral nerve
Superior gluteal nerve
Obturator nerve
Lateral femoral cutaneous nerve
Sciatic Nerve
Incidence
Most common nerve injury after THA (90%)
- incidence sciatic nerve injury 13,000 THA
- posterior approach 0.1%
- anterior approach 0.17%
Slaven et al J Arthroplasty 2023
- incidence sciatic nerve motor palsy in 10,000 primary THA
- posterior approach 0.46%
- anterior approach 0.05%
- full recovery of motor strength in 60%
Anatomy
L4/5 S1-3
- emerges at greater sciatic notch
- usually tibial and peroneal components combined
- runs below piriformis and above short external rotators (90%)
Variations (10%)
- CPN exits through piriformis muscle
- need to be careful before dividing piriformis in posterior approach
CPN division more vunerable to injury as tethered at fibular neck
Mechanism of injury
Traction - > 4cm lengthening in DDH
Posterior approach / posterior retractors
Postoperative haematoma (CT scan)
Wires / cables around femur
Revision surgery
DDH, protrusio - nerve in abnormal position
Management
Hematoma
- CT may be useful to diagnose
- washout
Recovery
Slaven et al J Arthroplasty 2023
- sciatic nerve motor palsy after primary THA
- full recovery of motor strength in 60%
- CPN injury following THA
- 14/25 incomplete injuries recovered completely by 1 year
- 3/5 complete injuries recovered completely by 18 months
Neurolysis
- 12 cases of sciatic nerve palsy following THA
- neurolysis at 6 months
- all patients experienced improvement in motor function
Femoral Nerve
Incidence
Slaven et al J Arthroplasty 2023
- incidence femoral nerve motor palsy in 10,000 primary THA
- posterior approach 0.06%%
- anterior approach 0.2%
- full recovery of motor strength in 60% of cases
Fleischman et al J Arthroplasty 2018
- incidence of femoral nerve injury 0.2%
- anterior approach 0.4%
- anterolateral approach 0.6%
Anatomy
Posterior divisions of L2-4
- enters femoral triangle between psoas and iliacus
Mechanism of injury
Anterior approach - anterior retractors above psoas
Iliacus hematoma
Cement extrusion / screws anterosuperior quadrant
Management
Fleischman et al J Arthroplasty 2018
- incidence of femoral nerve injury 0.2%
- no recovery until 6 months post injury
- persistent mild weakness in 25% at 3 years post injury
- persistent sensory disturbance in 80%
Superior Gluteal Nerve
Anatomy
L4/5 S1
- exits sciatic notch above piriformis
- runs between Gluteus medius and minimus
- supplies Gluteus medius / minimus & tensor fascia lata (TFL)
Mechanism of injury
Anterior / Smith Petersen approach
- anterior retractors
- cautery of the lateral circumflex femoral artery
- may affect branch to TFL
Lateral / Hardinge approach
- respect safe zone in Gluteus medius 3-5 cm proximal to greater trochanter
Incidence
- EMG following direct lateral approach for 40 THA
- 43% evidence of SGN injury at 4 weeks
- one positive trendelenberg test at 1 year
Takada et al J Orthop Sci 2018
- 30 bilateral THA randomized to direct anterior and anterolateral
- reduced bulk of TFL on CT with direct anterior approach
Obturator Nerve
Anatomy
Anterior division L2-L4
- along sacral alar
- emerge obturator foramen
Medial thigh parathesia / adductor weakness / persistent groin pain
Mechanism of injury
Retractors
Cement extrusion
- 4 cases of obturator nerve injury following cement extrusion
Lateral femoral cutaneous nerve
Anatomy
L2 and L3 nerve roots
- on the anterior surface of the iliacus muscle within the iliac fascia
- enters the thigh medial to the anterior superior iliac spine
- passes over the sartorius muscle before branching
Sensory only
Etiology
Direct anterior approach
Incidence
- 32% incidence in 122 direct anterior THA
- 132 anterior THA
- 81% had LFCN parasthesia postoperatively
- more common with hip resurfacing than conventional THA
Outcome
Bhargava et al Orthopedics 2010
- 81 hips with direct anterior THA
- 15% had LFCN parasthesia postoperatively
- 83% resolved by 2 years