complicated back pain..help

Hi guys,
really hope someone can throw some light on this one for me...am seeing a young boy, just turned 15years, big into sport playing soccor and basketball, and also rugby at a high level.

HPC; 2/years ago had bad tackle in rugby, where the low back was forced into hyperextension. At the time continued to play match as didnt want to go to hospital (was told ambulance was on the way) and was captain of the team. Was able to play but with pain. No x-ray following this. Since then experiencing intermittent pain in low back, with altered sensation into feet and lower legs, this is intermittent, doesnt always come on with back pain. Pain reproduced with lumbar ext only, VAS 6/10 at worst.
AGGS; Throwing in a side line ball in soccor, throwing ball over head in basketball.
EASES; nothing specific, flexion of low back

SOC; playing soccor, rugby at the moment and returning to basketball once school starts back. Training 4-5 days a week and then matches on top of that. Doing alot of gym work, weights and strengthening for rugby.

Has had previous Rx for groin strains (x2), back pain (where STM to erector spinae reieved pain).

No pattern day/night, general health good, no red flags

AROM; hyper extends from Lx spine on extension, pain at EOR. Good range in Flex/SF/Rot with no pain

NEURO; slump - +ve. with burning sensation into toes. SLR - c/o burning sensation into shin and foot. Dermatomes and myotomes fine. Reflexes- increased response in lower limb, normal in upper limbs.

PALPATION; TrP in erector spinae, spasm almost of the muscle, left greater than right side.PA's stiff in Lx spine, with pain on PA of L4.
Hams - SLR 45degrees on both side, has tight groin (prev hx of strains), and tight quads.

IN STANDING; he cannot stand up straight, when standing must have one leg bent slightly to prevent pain coming on in back...so generally stands with back stright and one leg out in front slight with knee and hip slightly flexed (hope that makes sense).

I have sent him for an xray to rule out damage to pars interarticularis...as i guess that was my initial thought, that perhaps he had a small fracture when he was tackled, and also due to the fact that low Lx ext causes his pain. I have not received results from this yet. At the moment attempting to relieve TrPs in erector spinae but they are so tight in general and really feel like they are spasming. His low body musculature is so tight, so we are working on stretching and increasing flexibility. I initailly met him for a grain strain but that has healed now. I have confined him to stationary bike training until we get xray result.

I guess i just want anyones take on this. Theres so much going on im not sure where to start.

Any advice greatly appreciated
E